Contract Ref.: AFCD/SQ/264/17/C

Mai Po Inner Deep Bay Ramsar Site Waterbird Monitoring Programme 2018 - 19

Egretry Counts in Hong Kong, with particular reference to the Mai Po Inner Deep Bay Ramsar Site

Summer 2019 Report

Submitted by The Hong Kong Bird Watching Society

to Agriculture, Fisheries and Conservation Department, Hong Kong SAR Government

February 2020

Printed on Recycled Paper Contract Ref.: AFCD/SQ/264/17/C Waterbird Monitoring at the Mai Po Inner Deep Bay Ramsar Site 2018-19

Waterbird Count Coordinator YU Yat Tung The Hong Kong Bird Watching Society

Report Writing and Data Contributors Captain L.C. WONG, TAM Yip Shing, Josephine Y.P. WONG, Luke, C.K. WOO, Louis, C. L. FUNG, CHEUNG MOK, Jose Alberto and Ching Yuen HO Egret Research Group, The Hong Kong Bird Watching Society

Copyright The project is part of the “Mai Po Inner Deep Bay Ramsar Site Waterbird Monitoring Programme 2018-19” of Agriculture, Fisheries and Conservation Department, Hong Kong SAR Government. All the data shall be the property of the Government with full copyright

Report is available for public information at Agriculture, Fisheries and Conservation Department Hong Kong SAR Government 7/F, Cheung Sha Wan Government Offices 303 Cheung Sha Wan Road Kowloon, Hong Kong Email: [email protected] Website: www.afcd.gov.hk

and

The Hong Kong Bird Watching Society 7C, V Ga Building, 532 Castle Peak Road Lai Chi Kwok, Kowloon, Hong Kong E-mail: [email protected] Website: www.hkbws.org.hk

This publication should be cited as Anon, 2020. Summer 2019 Report: Egretry Counts in Hong Kong with particular reference to the Mai Po Inner Deep Bay Ramsar Site. Report by The Hong Kong Bird Watching Society to the Agriculture, Fisheries and Conservation Department, Hong Kong Special Administrative Region Government.

2 TABLE OF CONTENTS

A report of Egretry Counts in Hong Kong, with particular reference to the Mai Po Inner Deep Bay Ramsar Site Summary 4 1. Introduction 4 2. Methods 5 3. Results and Discussion 5 3.1 Breeding population in the 2019 breeding season 5 3.2 Colonies in the Deep Bay area 8 3.3 Comparison of the number of nests with records of the previous year 10 3.4 Nesting substrates 11 3.5 Nest abandonment at A Chau 13 3.6 Disturbance at Penfold Park 13 3.7 Urgent tree works and associated disturbance at Mai Po Village 13 3.8 Site formation at Tai Tong 13 3.9 Tree pruning during the breeding season 14 4. Conclusion 14 5. Acknowledgements 14 6. References 14

TABLES Table 1. The number of nests at surveyed colonies in Hong Kong in 2019 7 Table 2. The relative importance of the Deep Bay colonies comparing to the other colonies in Hong Kong in 2019 8 Table 3. The number of nests recorded at the Deep Bay from 2010 to 2019 9 Table 4. A comparison of the number of nests in Hong Kong in 2018 and 2019 10 Table 5. A comparison on the number of nests of individual colony between 2018 and 2019 10 Table 6. Plant species utilized by ardeids as nesting substrates in 2019 11

FIGURES Figure 1. Location of nesting colonies (egretries) in Hong Kong in 2019 Figure 2. Total number of ardeid nests in Hong Kong with reference to the number of nests in the Deep Bay area from 2010 to 2019

APPENDICES Appendix 1. Survey date(s) of nesting colonies and additional sites in 2019 Appendix 2. The number of nests recorded in each monthly count of the 22 colonies in 2019

3 EGRETRY COUNTS IN HONG KONG, WITH PARTICULAR REFERENCE TO THE MAI PO INNER DEEP BAY RAMSAR SITE

SUMMER 2019 REPORT

Summary

In the 2019 breeding season (April to July), a total of 1,081 nests of five ardeid species, i.e. the Great Egret (Ardea alba), Little Egret (Egretta garzetta), Black-crowned Night Heron (Nycticorax nycticorax), Chinese Pond Heron (Ardeola bacchus) and Eastern Cattle Egret (Bulbulcus coromandus), were recorded in nine egretries (hereinafter referred to as ‘colonies’) in the Deep Bay area. The number of nests in this area accounted for 66% of the total number of nests in Hong Kong. The Chinese Pond Heron was the dominant species in the Deep Bay area, accounting for 28% of the total number of nests in this area. A total of 1,633 nests of the above-mentioned five species in 22 colonies were recorded in Hong Kong in 2019. Although about one third of the total number of nests in Hong Kong were not identified to species level, the Little Egret (27%) was the dominant species breeding in Hong Kong, while the Eastern Cattle Egret (1.5%) was the least abundant one. Compared with the 2018 records (505 nests in the Deep Bay area and 1,082 nests in Hong Kong), there was a 114% and 51% increase in the number of nests recorded in the Deep Bay area and Hong Kong, respectively. The increases were mainly due to the better estimation of nest abundance at the Mai Po Mangrove colony. A colony at San Sang San Tsuen was abandoned in this year, while the Little Green Island colony was active again. A colony at Shan Pui River was first included in this monitoring.

1 INTRODUCTION Following the establishment of the Mai Po Inner Deep Bay Ramsar Site, a long-term waterbird monitoring programme has been carrying out since 1998. The programme is coordinated by the Hong Kong Bird Watching Society (HKBWS) and is currently a commissioned study of the Agriculture, Fisheries and Conservation Department (AFCD) of the Hong Kong SAR Government. Under the Waterbird Monitoring Programme, egretry counts are conducted with an aim to record the population of tree-nesting ardeids, in terms of the number of nests in the Deep Bay area and elsewhere in Hong Kong. The present report documents the results of the egretry count between April and July 2019. A review of the nesting ardeids in Hong Kong between the 1950s and 1990s can be found in Young and Cha (1995), while the trends and their relationship with weather was documented in Wong and Young (2006).

2 METHODS Active and abandoned colonies identified in the past three years (2016 - 2018) were surveyed once per month between April and July 2019 (Table 1, Figure 1, Appendix 1). A nesting colony of egrets and herons is defined as an area in which more than one pair of these birds are recorded building nests, laying eggs and raising young. Colonies shrinking in size as compared to previous years with only one nest were also included. Active nests, determined by the presence of incubating adults or chicks,

4 were counted directly from vantage points along the edge of a colony with the use of 8-10x binoculars or by the naked eye, depending on the proximity between the surveyor and the colony. In case nests were hidden in vegetation which made the counting difficult, their numbers were estimated. In this case, landing locations were marked on a sketch and repeated landings around the same location were considered as a nest. This methodology was adopted for the Sha Chau, A Chau, Mai Po mangrove and Ma Wan colonies, where most of the nests were hidden in vegetation. Estimation of nests based on the position of newly fledged chicks was also used during the latter part of breeding season. As the colony at the Mai Po mangrove is very remote, it was counted from a vantage point which was 2.5 km away from the colony at Tsim Bei Tsui. Aerial photos of this colony were also taken in May, and estimation of the number of nest was later undertaken through desktop examination. The highest count of the number of nests of a particular species recorded during the survey period was taken as the number of nests of that species of the egretry. In addition to the number of nests, the nesting substratum was examined in most of the colonies that were accessible. Nomenclature of egrets and herons follows the annotated checklist of birds of Hong Kong (Hong Kong Bird Watching Society, 2017).

Both existing and new nesting colonies, if any, were monitored. New nesting colonies were identified by personal observations of the surveyors or through information provided by birdwatchers, the general public or AFCD. A nesting site would be considered as a new nesting colony if it was at least 500 m away from an existing colony, since the lowest foraging range of a colony is usually about 500 m (L. C. Wong, unpublished data). Combining breeding birds in locations within 500 m could avoid having to define too many small nesting sites in the same area.

3. RESULTS and DISCUSSION 3.1 Breeding population in the 2019 breeding season A total of 1,633 nests were recorded in 22 colonies in Hong Kong (Table 1, Figure 1, Appendix 2). A colony at Shan Pui River was first included in the monitoring this year. The Little Green Island colony was active only in July this year. It was abandoned in 2018. The colony at San Sang San Tsuen was abandoned. Highlights of the present breeding season were as follows:

· The Mai Po mangrove colony was the largest in Hong Kong, with 557 nests, about 34.1% of the total number of nests in Hong Kong. The colony split to two sub- colonies and showed a shift in location this year. A more accurate estimate of number of nest was possible due to the use of drone for monitoring.

· A colony mostly consisted of Chinese Pond Herons at Shan Pui River was first included in the monitoring.

5 · The Little Green Island colony was not active until July. Late commencement of breeding similar to this observation has not been noted since the monitoring commenced in 1998. This colony was abandoned in 2018.

· Although only one nest of Chinese Pond Heron was counted at the Tai Tong (Pak Sha Tsuen) colony, supplementary surveys undertaken by the AFCD revealed two nests (1 Little Egret and 1 Eastern Cattle Egret) were present during the breeding season. In order to standardize the survey effort and avoid inconsistency, these two nests were not included. Nevertheless, these records were documented here for reference.

· Abandonment of the colony at San Sang San Tsuen was noted. The vegetation was intact and nearby areas were undisturbed. No vandalism was noted at these colonies. The abandonment may be a natural event.

· Nest abandonment at A Chau during the breeding season was observed in this year again. Nesting activities (incubation and presence of chicks) were last seen on 18 May, and abandonment was seen on 20 May. Subsequent aerial inspection revealed that eggs were present at some of these abandoned nests, which may suggest that human disturbance can be excluded as a cause of abandonment. This was the second year which such abrupt abandonment of nests was recorded at A Chau.

· Abandoned colonies in previous years at Mai Po Nature Reserve, Tam Kon Chau, Pak Nai, Ting Kok (suspected colony) and Ngau Hom Sha were visited, but no breeding activity was recorded.

· Human activities were recorded at a few colonies and might have caused certain degree of disturbance to the breeding ardeids. Details can be found in section 3.6 -3.9.

· Typhoon Mangkhut passed near Hong Kong on 16 September 2018 and caused destruction of enormous number of trees in Hong Kong. The vegetation of a number of colonies were affected. Some have thinner vegetation as compared to previous breeding season while other have a number of trees fell. Thinning of vegetation at or near the colonies was obvious at Mai Po Village, Sha Kiu Village, Tung Shing Lane, Tai Po Market, Man Kam To Road, Tuen Mun and Penfold Park. This might affect the use of these location as breeding sites by the ardeids.

The largest colony in Hong Kong was the Mai Po mangrove colony (557 nests, 34.1% of total nests recorded in Hong Kong). It is estimated that the dominant species was the Great Egret and a smaller number of Black-crowned Night Herons was also present. This colony was surveyed by two methods: (1) distant observation from a vantage point which was 2.5 km away from the colony at Tsim Bei Tsui and (2) aerial photos taken by drone at height of 70 m or above. Owing to the limitation of both methods, most nests could not be identified to the species level. However, it was

6 confirmed that Great Egrets, Little Egrets, Eastern Cattle Egrets and Black-crowned Night Herons were breeding at this colony. Although the exact number of nest for each species could be not counted, this colony probably supported the highest number of nests of Great Egret in Hong Kong. The second largest colony was the Tai Po Market colony (206 nests, 12.6% of the total number of nests in Hong Kong). Disregarding the unidentified nests, Tai Po Market colony supported the highest number of nests of Great Egrets (40 nests, 37.4% of the total number of nests of this species in Hong Kong), Little Egret (92 nests, 21.1% of the total number of nests of this species in Hong Kong) and Black-crowned Night Herons (74 nests, 43.0% of the total number of nests of this species in Hong Kong). The third largest colony was the Mai Po Village colony (159 nests, 9.7% of the total number of nests in Hong Kong). The Shan Pui River colony supported the largest abundance of nests of Chinese Pond Herons (86 nests, 24.2% of the total number of nests of this species). The Ho Sheung Heung colony supported the highest number of nests of Eastern Cattle Egrets (15 nests, 62.5% of the total number of nests of this species). The lowest number of nests was recorded at the Ha Che colony and the Tai Tong colony (1 nest each, 0.1% of the total number of nests in Hong Kong). Nevertheless, it should also be noted that 4 nests of Chinese Pond Heron were recorded by AFCD at Ha Che colony outside this monitoring programme.

Regarding the number of nests recorded for each species, Little Egret was the most abundant (435 nests, 26.6% of the total number of nests), and widespread species (17 out of 22 colonies). The Eastern Cattle Egret was the least abundant (24 nests, 1.5%) and most restricted species (3 out of 22 colonies). It should be noted that one third of the nests recorded this year (540 nests at Mai Po mangrove colony) were not identified to species level.

Table 1. The number of nests at surveyed colonies in Hong Kong in 2019. Black- Chinese Eastern Great Little crowned Un- Total Pond Cattle % Rank Egret Egret Night identified Heron Egret Heron Deep Bay area 1. Mai Po Village 91 68 159 9.7 3 2. Mai Po Lung Village 41 68 109 6.7 4 3. Tung Shing Lane 27 38 65 4.0 7 4. Ngau Hom Shek 9 18 27 1.7 12 5. Pak Nai 2 22 1 23 1.4 14 6. Shenzhen Bay Bridge 20 10 30 1.8 11 7. Sha Kiu Village 10 10 20 1.2 17 8. Mai Po mangrove^ 6 5 2 4 540 557 34.1 1 9. Shan Pui River 5 86 91 5.6 5 Elsewhere in the New Territories

7 10. Ho Sheung Heung 3 3 15 21 1.3 15 11. Man Kam To Road 28 34 62 3.8 8 12. Ping Che 11 11 0.7 20 13. Tai Tong (Pak Sha 1 1 0.1 21 Tsuen)# 14. Tai Po Market 40 92 74 206 12.6 2 15. Tuen Mun 14 14 0.9 19 16. Penfold Park 21 25 25 6 77 4.7 6 17. A Chau* 21 21 1.3 15 18. . Sha Chau* 14 23 16 53 3.2 9 19. Ma Wan* 5 12 22 5 44 2.7 10 20. Ha Che+ 1 1 0.1 21

Kowloon

21. Kowloon Park 26 26 1.6 13

Hong Kong Island

22. Little Green Island 8 7 15 0.9 18

Total 107 435 172 355 24 540 1,633 100

% 6.6 26.6 10.5 21.7 1.5 33.1 100

Note: * Some nests at the A Chau, Sha Chau, and Ma Wan were found in dense vegetation and may have been overlooked. The number of nests might have been underestimated. ^ Aerial photos of the Mai Po mangrove colony were taken for estimation of the number of nests. Special care was taken during the photo taking session to minimize disturbance to the breeding ardeids. # One nest of Little Egret and one nest of Eastern Cattle Egret in May were recorded by AFCD at Tai Tong (Pak Sha Tsuen) colony outside this monitoring programme. + Four nests of Chinese Pond Heron were recorded in April by AFCD at Ha Che colony outside this monitoring programme.

3.2 Colonies in the Deep Bay area A total of 1,081 nests of five ardeid species was recorded in nine colonies within the Deep Bay area in the 2019 breeding season (Table 2). The 2019 count was the highest one in the last decade and doubled the number recorded in 2018 (Table 3). Such increase was due to the estimation of over 500 nests at the Mai Po mangrove colony by taking aerial photos with drone. In previous years, only direct observation from a distant vantage point was conducted for this colony. Therefore, it was capable to obtain a more accurate count of nests this year. The number of nests in the Deep Bay area was about two third of the total number of nests in Hong Kong. The Deep Bay colonies supported the majority of breeding Little Egrets (52.9%) and Chinese Pond Herons (84.2%), in terms of the number of nests identified to species level. Disregarding the unidentified nests, the Chinese Pond Heron was the dominant species, with 27.7% of the total number of nests, in the Deep Bay area.

8

Table 2. The relative importance of the Deep Bay colonies compared to the other colonies in Hong Kong in 2019. (Colonies in the Deep Bay area included Mai Po Village, Mai Po Lung Village, Tung Shing Lane, Ngau Hom Shek, Pak Nai 2, Shenzhen Bay Bridge, Sha Kiu Village, Mai Po Mangrove and Shan Pui River) Deep Bay nests as No. of nests No. of nests in Species % of all nests in in Deep Bay Hong Kong Hong Kong Great Egret 6 107 5.6 Little Egret 230 435 52.9 Black-crowned Night 2 172 1.2 Heron Chinese Pond Heron 299 355 84.2 Eastern Cattle Egret 4 24 16.7 Unidentified 540 540 100.0 Total 1,081 1,633 66.2

A summary of the number of nests of the five ardeid species recorded in the Deep Bay area in the last decade (i.e. from 2010 to 2019) is shown in Table 3. The nest abundance in 2019 was almost double that of 2018 due to the presence of a vast number of unidentified ones at the Mai Po mangrove colony. As the accessibility of this colony is very poor, no ground survey could be made. Aerial photos taken at a height of at least 70 m were used to estimate the nest abundance, but the resolution of the photos was not high enough for species identification. Compared with last year, the number of nest of Great Egret and Black-crowned Night Heron declined, while Chinese Pond Heron and Eastern Cattle Egret increased. Nevertheless, it was estimated that many unidentified nests probably were nest of Great Egret and Black- crowned Night Heron. The number of nests of Little Egret in 2019 was the same as in 2018.

Table 3. Number of nests recorded in the Deep Bay area from 2010 to 2019. Black- Chinese Eastern Great Little crowned Unidentifie Total no. of nests Pond Cattle Egret Egret Night d in Deep Bay Heron Egret Heron 2010 85 163 248 2011 133 154 287 2012 97 176 273 2013 91 168 259 2014 1 190 227 418 2015 163 260 72 295 12 802 2016 100 188 27 297 8 620

9 2017 42 190 6 299 537 2018 13 230 4 256 2 505 2019 6 230 2 299 4 540 1,081

3.3 A comparison of the number of nests with records of the previous year When compared with the results in the whole of Hong Kong in 2018, the number of nests of Great Egret and Chinese Pond Heron showed a minor increase, while that of Little Egret, Black-crowned Night Heron and Eastern Cattle Egret showed a minor decrease (Table 4). The minor increase and decrease may just a natural fluctuation. Nevertheless, it should be noted that about one third of the total number of nests were unidentified (see Section 3.1 and 3.2).

Table 4. A comparison of the number of nests in Hong Kong in 2018 and 2019. 2018 2019 Percentage change (%) Great Egret 98 107 9.2 Little Egret 449 435 -3.1 Black-crowned Night Heron 184 172 -6.5 Chinese Pond Heron 323 355 9.9 Eastern Cattle Egret 28 24 -14.3 Unidentified nests --- 540 NA Sub-total in Deep Bay 505 1,081 114.1 Total in Hong Kong 1,082 1,633 50.9

When comparing the number of nests in individual colonies between 2018 and 2019, 11 colonies had more nests in 2019 than 2018, while nine colonies had fewer nests (Table 5). One colony (San Sang San Tsuen) was abandoned, while one colony (Little Green Island) was active again. An increase in number of nests at Mai Po Lung Village was noted, while a decline was noted at Mai Po Village. It is suspected movement of breeding birds in-between these two colonies might have occurred as they were in close proximity. This might be due to the destruction of vegetation at Mai Po Village due to Typhoon Mangkhut in 2018. Similar movement might have occurred between Ho Sheung Heung and Man Kam To Road.

Table 5. A comparison of the number of nests of individual colony between 2018 and 2019 (N.A.: Not applicable) Change Change 2018 2019 (%) 2018 2019 (%) Mai Po Village 222 159 -28.4 Man Kam To Road 39 62 59.0 Mai Po Lung Village 67 109 62.7 Ping Che 9 11 22.2 Tung Shing Lane 84 65 -22.6 A Chau 16 21 31.3 Ngau Hom Shek 19 27 42.1 Ha Che 15 1 -93.3 Pak Nai 2 18 23 27.8 Tai Po Market 195 206 5.6

10 Shenzhen Bay Bridge 27 30 11.1 Tuen Mun 20 14 -30.0 Sha Kiu Village 27 20 -25.9 Penfold Park 73 77 5.5 San Sang San Tsuen 1 0 -100.0 Sha Chau 82 53 -35.4 Mai Po Mangrove 40 557 1292.5 Ma Wan 31 44 41.9 Ho Sheung Heung 37 21 -43.2 Kowloon Park 48 26 -45.8 Tai Tong (Pak Sha Little Green Island 0 15 100.0 12 1 -91.7 Tsuen) Shan Pui River - 91 100.0

3.4 Nesting substrates Bamboo was the main nesting substrate for egrets and herons nesting in the north and northwest New Territories. It was used in 9 out of the 22 colonies (Table 5). The mangrove species, Kandelia obovata, was the main nesting substrate of the Mai Po Mangrove and A Chau colonies. Birds at the Penfold Park colony and Shan Pui River colony built their nests on Banyan trees (Ficus microcarpa). The exotic tree Acacia auriculiformis was used as nesting substrate by ardeids in the Tuen Mun colony. Most nests in Mai Po Village were built on Chinese Hackberry (Celtis sinensis) and Banyan Tree (Ficus microcarpa). Large Ficus trees at Kowloon Park were used by Black- crowned Night Herons as nesting substrates.

Table 6. Plant species utilized by ardeids as nesting substrates in 2019 Site Site Bamboo Tree species Remarks 1 Mai Po Village + Albizia lebbeck Aleurites moluccana Celtis sinensis Dimocarpus longan Ficus microcarpa Melaleuca cajuputi subsp. cumingiana Melia azedarach 2 Mai Po Lung Village Ficus benjamina Ficus microcarpa Ficus virens Litchi chinensis

3 Tung Shing Lane + Celtis sinensis Dimocarpus longan Ficus microcarpa Macaranga tanarius var. tomentosa Melia azedarach 4 Ngau Hom Shek +

11 5 Pak Nai 2 + 6 Shenzhen Bay Bridge + 7 Sha Kiu Village Celtis sinensis 8 Shan Pui River Ficus microcarpa 9 Mai Po mangrove Kandelia obovata 10 Ho Sheung Heung + Cleistocalyx nervosum Dimocarpus longan Sterculia nobilis 11 Man Kam To Road Acacia auriculiformis Bischofia javanica Callistemon viminalis Celtis sinensis Ficus microcarpa Ficus virens Senna siamea 12 Ping Che + 13 A Chau Kandelia obovata 14 Tai Tong + (Pak Sha Tsuen) 15 Tai Po Market Ficus variegata Macaranga tanarius Celtis siensis Mangifera indica 16 Ha Che Ficus microcarpa 17 Tuen Mun Acacia auriculiformis 18 Penfold Park Ficus microcarpa 19 Sha Chau No observation was made 20 Ma Wan No observation was made 21 Kowloon Park Ficus microcarpa Ficus binnendijkii 22 Little Green Island No observation was made

12 3.5 Nest abandonment at A Chau The A Chau colony was once the largest in Hong Kong in the 2000s. In the breeding seasons of 2018 and 2019, nest abandonment was noted around mid-May. In 2019, the abandonment should occur between 18 and 20 May as breeding birds were seen on 18 May but only empty nests were seen on 20 May. Aerial photos taken by AFCD in late May showed that eggs were seen in some of these abandoned nests and damages to vegetation was not observed. This might reflect that vandalism due to human disturbance (e.g. collection of eggs) could be excluded as a cause of abandonment. Besides, the wetland feeding habitats are still present around the nesting colony. Therefore, it is suspected that other environmental or biological factors, for instance low prey availability, may contribute to the nest abandonment.

From the long-term wetland management point of view, it is suggested that a holistic approach of managing and monitoring of wetlands in Starling Inlet can be considered.

3.6 Disturbance at Penfold Park Dredging and draining works was first observed at the lake at Penfold Park where the colony was situated by AFCD in mid-May. Both AFCD and HKBWS contacted the concerned party and requested a suspension of works or other measures to minimize the disturbance to the breeding birds. During the monitoring on 23 May, works was still underway. Although part of the nesting area was fenced off, such area was too small to avoid and reduce human disturbance. With the continuous communication of AFCD and HKBWS with other concerned parties, the works was finally suspended and the lake was reinstated in late May. The monitoring in June and July revealed that more ardeids returned to this nesting area and bred.

3.7 Urgent tree work and associated disturbance at Mai Po Village On 30 April 2019, urgent tree work was undertaken at this colony as a branch of a tree used by the ardeids for nesting was broken and hung above the road. Fallen chicks were reported at the colony before the tree works. On site monitoring of the egretry was conducted continuously during the removal of the hanging branch. Nevertheless, disturbance to the birds was inevitable. Measures were taken to minimize such disturbance, e.g. shorten the duration of the work and reduce the number of workers entering the colony as far as possible.

Caution should be taken seriously when undertaking urgent works at egretry during the breeding season. Human activities inside the colony would cause disturbance to parent birds and they may not fly back to their nests to feed their young. Chicks may also fall from the nests. Only trained person should be allowed to work in a colony as they know the behaviour of the birds and process the skill of bird handling. The condition of the birds and the reaction of the birds to the works should be taken into account for working out the best way to conduct the works and the bird rescue.

3.8 Site formation at the Tai Tong colony Site formation works was noted close to this colony in May. The area was paved and hoarding was erected. Only one nest was found during monitoring this year. The

13 disturbance of the works nearby might be related to the reduced number of nests at this colony.

3.9 Tree pruning during the breeding season Hard pruning of trees was noted in the Tung Shing Lane colony during the monitoring in May. These affected areas were known to be within the nesting area in previous years. The degree of disturbance to the breeding ardeids was uncertain.

4. CONCLUSION In 2019, a total of 1,633 nests of five species in 22 colonies were recorded in Hong Kong, including 1,081 nests of five species in nine colonies in the Deep Bay area. One colony (San Sang San Tsuen) was abandoned and one (Little Green Island) was active again. A colony at Shan Pui River was first included in the monitoring. Disturbance was noted in a few colonies. When compared to the results in 2018, there was a 114% and 51% increase in the number of nests in Deep Bay area and Hong Kong, respectively. While there might be a genuine increase in the number of nests, the better estimation of nest abundance at the Mai Po mangrove colony by the use of aerial photos might have contributed to this result as well.

5. ACKNOWLEDGEMENTS We would like to thank Rachel Poon, Niki Wong, Stanley Chan and Evans Leung who assisted in the survey. Gratitude should also be expressed to the landowner (Mrs Cheng) next to the Ha Che colony for allowing us to conduct the survey at her property. We would also like to thank input and contribution from AFCD, and the Marine Parks Division of AFCD for the arrangement of vessel for the surveys at Sha Chau. Last but not least, we would like to particularly thank Helen Fong of the HKBWS office for her kind coordination.

6. REFERENCES Hong Kong Bird Watching Society, 2019. ‘HK_List_2018-04-25.pdf’ [online]. Available from: http://www.hkbws.org.hk/BBS/viewthread.php?tid=27461 [Accessed August 2019]. Wong L. C., R. T. Corlett, L. Young and J. S. Y. Lee. 1999. Foraging Flights of Nesting Egrets and Herons at a Hong Kong Egretry, South China. Waterbirds 22: 424- 434 Wong, L.C. and L Young. 2009. Coastal wetlands in Ecology of the Birds of Hong Kong (Wong L. C., V. W. Y. Lam and G. W. J. Ades Eds). Kadoorie Farm and Botanic Garden, HKSAR Young, L. and M.W. Cha. 1995. The history and status of egretries in Hong Kong with notes on those in the Pearl River delta, Guangdong, China. Hong Kong Bird Report 1994: 196-215.

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Summer 2019 Report: Egretry Counts in Hong Kong with particular reference to the Mai Po Inner Deep Bay Ramsar Site

Figures

The Hong Kong Bird Watching Society

Agriculture, Fisheries and Conservation Department

15 Figure 1. Location of the 22 colonies in Hong Kong in 2019. (The enclosed is the Deep Bay colonies) 1 Mai Po Village 2 Mai Po Lung Village 3 Tung Shing Lane 4 Ngau Hom Shek 5 Pak Nai 2 6 Shenzhen Bay (Tin Hau Temple) Bridge 7 Sha Kiu Village 8 Mai Po Mangrove 9 Shan Pui River 10 Ho Sheung Heung 11 Man Kam To Road 12 Ping Che 13 Tai Tong 14 Tai Po Market 15 Tuen Mun (Pak Sha Tsuen) 16 Penfold Park 17 A Chau 18 Sha Chau 19 Ma Wan 20 Ha Che 21 Kowloon Park 22. Little Green Island

16 Figure 2. A 10-year summary of the total number of ardeid nests in Hong Kong with reference to the number of nests in the Deep Bay area from 2010 to 2019.

1800 1633 Deep Bay 1600 Hong Kong 1418 1400 1248 1245

1200 1082 960 1000 1081 852 799 758 800 734

No ofNonests 802 600 620 537 400 505 418 200 287 248 273 259

0 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 Year

17 Appendix 1. Survey date(s) of nesting colonies and additional sites in 2019.

Colony Date Active colonies 1. Mai Po Village* 14 Apr, 12 May, 15 Jun, 14 Jul 2. Mai Po Lung Village* 21 Apr, 13 May, 7 Jun, 1 Jul 3. Tung Shing Lane* 21 Apr, 13 May, 7 Jun, 1 Jul 4. Ngau Hom Shek* 14 Apr, 12 May, 15 Jun, 14 Jul 5. Pak Nai 2* 14 Apr, 12 May, 15 Jun, 14 Jul 6. Shenzhen Bay Bridge* 14 Apr, 12 May, 15 Jun, 14 Jul 7. Sha Kiu Village* 14 Apr, 12 May, 15 Jun, 14 Jul 14 Apr, 12 and 30 May1, 15 Jun, 14 8. Mai Po Mangrove* Jul 9. Shan Pui River*2 25 May, 12 and 15 Jun3, 4 and 14 Jul3 10. Ho Sheung Heung 21 Apr, 13 May, 7 Jun, 1 Jul 11. Man Kam To Road 21 Apr, 13 May, 7 Jun, 1 Jul 12. Ping Che 13 Apr, 18 May, 8 Jun, 6 Jul 13. Tai Tong (Pak Sha Tsuen) 21 Apr, 13 May, 7 Jun, 1 Jul 14. Tai Po Market 13 Apr, 18 May, 8 Jun, 6 Jul 15. Tuen Mun 13 Apr, 24 May, 8 Jun, 6 Jul 16. Penfold Park 13 Apr, 23 May, 14 Jun, 6 Jul 17. A Chau 13 Apr, 18 May, 8 Jun, 6 Jul 18. Sha Chau 13 Apr, 17 May, 8 Jun, 6 Jul 19. Ma Wan 29 Apr, 27 May, 25 Jun, 9 Jul 20. Ha Che 13 Apr, 18 May, 8 Jun, 6 Jul 21. Kowloon Park 13 Apr, 2 May, 12 Jun, 4 Jul 22. Little Green Island 18 Apr, 16 May, 14 Jun, 14 Jul

Previously active/additional sites 23. Tsim Bei Tsui* 14 Apr, 12 May, 15 Jun, 14 Jul 24. Lam Tsuen 2 13 Apr, 18 May, 8 Jun, 6 Jul 25. Ngau Hom Sha* 14 Apr 26. Tam Kon Chau* 14 Apr

18 27. Mai Po Marshes Nature 21 Apr Reserve* 28. Pak Nai* 14 Apr 29. The Chinese University of Hong 13 Apr, 18 May, 8 Jun, 6 Jul Kong 30. San Sang San Tsuen* 21 Apr, 13 May, 7 Jun, 1 Jul 31. Hung Hom4 19 Jun 32. Ting Kok 18 May

Remarks: * within the Deep Bay area 1: Aerial photo-taking by AFCD 2: This colony was first reported in May. Therefore, no April count was made. 3: Owing to site restriction, surveys were conducted on two days to count the nests in both June and July. 4: Juveniles of Black-crowned Night Heron were observed at Hung Hom in June with disused nests on the concerned trees. It was confirmed by AFCD that the disused nests were not nests of ardeids and the location was not an egretry.

19 Appendix 2. The number of nests recorded in each monthly count of the 22 colonies in 2019.

Appendix 2.1. Mai Po Village 14 Apr 12 May 15 Jun 14 Jul Max Little Egret 72 91 40 12 91 Chinese Pond Heron 68 56 26 16 68 Total 140 147 66 28 159

Appendix 2.2 Mai Po Lung Village 21 Apr 13 May 7 Jun 1 Jul Max Little Egret 16 14 41 31 41 Chinese Pond Heron 30 60 51 68 68 Total 46 74 92 99 109

Appendix 2.3 Tung Shing Lane 21 Apr 13 May 7 Jun 1 Jul Max Little Egret 24 27 24 8 27 Chinese Pond Heron 12 15 38 25 38 Total 36 42 62 33 65

Appendix 2.4 Ngau Hom Shek 14 Apr 12 May 15 Jun 14 Jul Max Little Egret 1 9 4 6 9 Chinese Pond Heron 7 10 18 14 18 Total 8 19 22 20 27

Appendix 2.5 Pak Nai 2 14 Apr 12 May 15 June 14 Jul Max Little Egret 22 12 22 Chinese Pond Heron 1 1 Total 22 13 nil nil 23

Appendix 2.6 Shenzhen Bay Bridge 14 Apr 12 May 15 Jun 14 Jul Max Little Egret 13 20 3 20 Chinese Pond Heron 10 10 Total 13 30 3 nil 30

20 Appendix 2.7 Sha Kiu Village 14 Apr 12 May 15 Jun 14 Jul Max Little Egret 10 6 5 3 10 Chinese Pond Heron 4 10 4 10 Total 14 16 9 3 20

Appendix 2.8 Mai Po Mangrove (* estimated based on aerial photos taken on 30 May 2019. Some unidentified nests were deducted from those identified by field survey.) 12 and 14 Apr 15 Jun 14 Jul Max 30 May Great Egret 1 4 6 3 6 Little Egret 5 5 3 5 Black-crowned Night 2 + 2 Heron Eastern Cattle Egret 4 1 1 4 Unidentified spp* 540 540 Total 6 555 10 4 557

Appendix 2.9 Shan Pui River (The site was first reported in May.) 12 and 4 and 14 25 May Max 15 Jun Jul Little Egret 5 5 Chinese Pond Heron 86 66 38 86 Total 86 66 43 91

Appendix 2.10 Ho Sheung Heung 21 Apr 13 May 7 Jun 1 Jul Max Little Egret 3 1 1 3 Chinese Pond Heron 3 3 3 Eastern Cattle Egret 10 13 15 15 Total 13 17 19 nil 21

Appendix 2.11 Man Kam To Road 21 Apr 13 May 7 Jun 1 Jul Max Little Egret 13 21 11 28 28 Chinese Pond Heron 9 30 34 15 34 Total 22 51 45 43 62

Appendix 2.12 Ping Che 13 Apr 18 May 8 Jun 6 Jul Max Chinese Pond Heron 3 11 9 9 11 Total 3 11 9 9 11

21 Appendix 2.13 Tai Tong (Pak Sha Tsuen) 21 Apr 13 May 7 Jun 1 Jul Max Chinese Pond Heron 1 1 1 Total 1 1 nil nil 1

Appendix 2.14. Tai Po Market 13 Apr 18 May 8 Jun 6 Jul Max Great Egret 12 40 38 17 40 Little Egret 66 92 66 43 92 Black-crowned Night 40 57 74 58 74 Heron Total 118 189 178 118 206

Appendix 2.15. Tuen Mun 13 Apr 24 May 8 Jun 6 Jul Max Little Egret 14 13 8 14 Total 14 13 8 nil 14

Appendix 2.16. Penfold Park 13 Apr 23 May 14 Jun 6 Jul Max Great Egret 21 14 10 4 21 Little Egret 25 3 15 19 25 Black-crowned Night 9 5 12 25 25 Heron Chinese Pond Heron 3 1 6 5 6 Grey Heron + + Total 58 23 43 53 77

Appendix 2.17 A Chau (*: No bird and nest were found after May, suggesting nest abandonment of active nests after the May count.) 13 Apr 18 May 8 Jun 6 Jul Max Great Egret 21 10 21 Total 21 10 nil nil 21

Appendix 2.18. Sha Chau 13 Apr 17 May 8 Jun 6 Jul Max Great Egret 14 10 6 2 14 Little Egret 22 23 17 1 23 Black-crowned Night 16 11 5 1 16 Heron Total 52 44 28 4 53

22 Appendix 2.19. Ma Wan 29 Apr 27 May 25 Jun 9 Jul Max Great Egret 5 5 1 5 Little Egret 12 9 3 3 12 Black-crowned Night 22 12 1 1 22 Heron Eastern Cattle Egret 5 3 5 Total 44 29 5 4 44

Appendix 2.20. Ha Che 13 Apr 18 May 8 Jun 6 Jul Max Chinese Pond Heron 1 1 1 Total nil 1 1 nil 1

Appendix 2.21. Kowloon Park 13 Apr 2 May 12 Jun 4 Jul Max Black-crowned 26 22 3 2 26 Night Heron Total 26 22 3 2 26

Appendix 2.22. Little Green Island 18 Apr 16 May 14 Jun 14 Jul Max Little Egret + 8 8 Black-crowned Night + 7 7 Heron Total nil nil nil 15 15

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